Polymer films are used in many fields for numerous different uses. Countless different properties are required or desirable depending on the applications in which the films are used. One of the many aesthetic and functional characteristics of a film is the presence and nature of text, images, indicia and other aspects of printed appearance. These function to provide identifying or other useful information or to give a particular appearance for visual appeal or other reasons. They are of particular use where the film is used in packaging.
Labels can be applied to numerous substrates in order to identify them, provide useful or identifying information, provide or enhance aesthetic qualities, provide or enhance eye appeal, seal or otherwise strengthen products or alter their physical properties.
Labels and stock for making labels can be made from a variety of materials including papers or films, including polymeric films. An adhesive is usually used to adhere a label to a substrate and typically the polymer film will comprise an adhesive layer on its back, such as a pressure sensitive adhesive layer, for this purpose.
Release liners are often used to protect the adhesive layer until it is desired to apply the label to a substrate or to render the label ready for this purpose. They also serve a useful purpose where labelstock is wound on reels in that they segregate the adhesive of one part of the labelstock from the top of another part of the labelstock. This can be important to protect not only the adhesive but also the top surface of the label. However the use of release liners is inherently wasteful and environmentally unsustainable. A release liner will typically comprise a support (for example made from paper or paper-based material or a polymer film) and a siliconised surface. The release liner is usually discarded after use meaning that considerable technology and valuable material is not used throughout the life cycle of the product, and having the further consequence that there is a large waste disposal burden.
Many different techniques can be used for printing or marking films used in or for labels. Traditionally, substrates have been marked by applying inks and using various printing techniques. For example, water based, solvent based or UV based technologies have been used, including for example flexographic (flexo), gravure, screen printing and rotary screen printing methods.
Whilst it is desirable to avoid the use of release liners, linerless facestock is not particularly suitable for printing.